rocketmq_filter/utils/
bloom_filter.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
use crate::utils::bloom_filter_data::BloomFilterData;

#[derive(Clone, Copy)]
pub struct BloomFilter {
    // as error rate, 10/100 = 0.1
    f: i32,
    n: i32,
    // hash function num, by calculation.
    k: i32,
    // bit count, by calculation.
    m: i32,
}

impl Default for BloomFilter {
    fn default() -> Self {
        BloomFilter {
            f: 10,
            n: 128,
            k: 0,
            m: 0,
        }
    }
}

impl BloomFilter {
    pub fn new(f: i32, n: i32) -> Result<Self, &'static str> {
        if !(1..100).contains(&f) {
            return Err("f must be greater or equal than 1 and less than 100");
        }
        if n < 1 {
            return Err("n must be greater than 0");
        }

        let error_rate = f as f64 / 100.0;
        let k =
            (0.5f64.log2() * (n as f64 * error_rate.ln()).abs() / error_rate.ln()).ceil() as i32;

        if k < 1 {
            return Err(
                "Hash function num is less than 1, maybe you should change the value of error \
                 rate or bit num!",
            );
        }

        let m = (n as f64 * error_rate.ln().abs() / (2f64.ln() * 2f64.ln())).ceil() as i32;
        let m = 8 * ((m + 7) / 8); // Ensure m is a multiple of 8

        Ok(BloomFilter { f, n, k, m })
    }

    pub fn f(&self) -> i32 {
        self.f
    }

    pub fn n(&self) -> i32 {
        self.n
    }

    pub fn k(&self) -> i32 {
        self.k
    }

    pub fn m(&self) -> i32 {
        self.m
    }

    pub fn is_valid(&self, filter_data: Option<&BloomFilterData>) -> bool {
        match filter_data {
            Some(data) => {
                data.bit_num() == self.m as u32 && data.bit_pos().len() == self.k as usize
            }
            None => false,
        }
    }
}